Does the Equal Protection Clause Require Local Police to Investigate and Prosecute Sexual Assault Crimes?

Over at Prawfs, Sam Bagenstos flags a new investigation by the DOJ Civil Rights Division:

Yesterday, the Division announced the opening of a novel joint investigation of the University of Montana (under Title IV of the Civil Rights Act of 1964 and Title IX of the Education Amendments of 1972), and the City of Missoula Police Department and the Office of the Missoula County Attorney (under the police misconduct provision of the 1994 Violent Crime Control and Law Enforcement Act and the antidiscrimination provision of the 1968 Safe Streets Act). The investigation will assess whether the University and the local authorities violated the Constitution or civil rights laws by failing to protect women against sexual assaults. In announcing the investigation, AAG Perez said that “[i]n the past three years, there have been at least 80 reported rapes in Missoula. At least 11 sexual assaults involving University students are alleged to have occurred in the past 18 months.” This investigation seeks to vindicate the constitutional guarantee of equal protection of the laws in its core, original sense — the guarantee that state and local law enforcement will protect all citizens equally against private depradations.

. . . [W]hat breaks new ground is not the investigation of the University — that’s standard fare for Title IX investigations — but the broader investigation of the local Missoula police and prosecutor’s office. This is the first Division law enforcement investigation of which I am aware in which the discriminatory failure to protect a class of victims of crime has been the main focus, and in which the Division has targeted prosecutors as well as police. This is, as I said, an effort to vindicate the equal protection of the laws in its core, original sense. Discriminatory failure to investigate and prosecute crimes has been a major problem for victims of sexual assault and violence against women (something the Supreme Court acknowledged, then disregarded, in United States v. Morrison). And, as Randy Kennedy’s work highlights, it has been a major problem for racial minorities who are victims of crime as well.

And DOJ is basically the only entity that can challenge these sorts of systemic patterns of discrimination in court. Discrimination is likely to be impossible to prove in any individual case. . . [I]n Missoula, any individual victim is likely to be unable to show that the police or proseuctors responded less vigorously to her crime because of her gender rather than because of the individual facts. . . .

So DOJ is likely the only entity that can bring these sorts of claims into court. I still wouldn’t underplay the difficulties of proof here. But the Civil Rights Division’s efforts to attack the problems of . . . failure to protect crime victims are incredibly important.

I favor aggressive investigation and prosecution of sexual assault crimes. With that said, I’m a bit puzzled by the legal theory animating DOJ’s investigation. If equal protection requires similar treatment of similar things, what is the standard for measuring whether sexual assault crimes are being treated equally? Do we compare prosecutions for sexual assaults in cases with female victims with prosecutions for sexual assaults in cases with male victims? Or do we compare prosecutions for sexual assaults as a whole with prosecutions for other crimes that are generally deemed equally serious? And if the latter, does that mean that the federal constitution’s Equal Protection clause mandates a particular approach to allocation of state and local law enforcement resources in sexual assault cases? This isn’t at all my area, so I’m not sure what to make of this. But at least at first blush, I’m not sure I see a proper role for federal intervention here.